Many projectors have limited dynamic range and hence finite black levels. When two projectors are arranged to project overlapping images for example, when tiling images, a blend zone can appear brighter than the adjacent non-blend regions. Such an effect can be particularly noticeable when each projector is projecting a respective image, each having a finite black level. For example, if each projector has a given finite black level, in the blend zone the black level will be a sum of the given finite black levels of each projector (e.g. 2X fL intensity, or twice the black level of the projectors, assuming each projector has the same given finite black level of “X”), which can result in the blend zone appearing gray.
One solution is to move fixed geometry neutral density filter assemblies in and out of a light path frustum from a lens of a projector, to attempt to create a non-distracting optical blend for dark scenes, which can work for night simulators and other situations with dark scenes. However, such a solution does not tend to work well with projectors much higher than 8000 lumens without overheating and distorting the filters, unless they are quite large and far away from the lens, which can be awkward to arrange.
Another solution, referred to as electronic blending, is to boost the black level electronically outside the blend zones to a higher gray level; however, such a solution reduces dynamic range. Hence, while such a solution can be used for scenes without much black content, it is not versatile.